strange slowness in connecting to google.com

[periz]

Hi. I'm running Mandriva 2010 on my desktop. I'm connected to internet through the network of my lab (dhcp). I cannot understand why, when I try to connect to google.com or related domains it takes up to 10 min to load the page...
Other webpages are loaded normally.
What's more incredible (at least to me) is that I've also established an adhoc wireless network with my notebook that is using my desktop as gateway and my notebook can load google.com at normal speed!!!

Here the output of tracepath google.com on my desktop
1: 192.168.20.51 (192.168.20.51) 0.117ms pmtu 1500
1: 192.168.20.254 (192.168.20.254) 0.272ms
1: 192.168.20.254 (192.168.20.254) 0.267ms
2: 137.189.161.252 (137.189.161.252) 1.212ms
3: 137.189.161.238 (137.189.161.23 1.072ms
4: no reply

here the output of tracert on my windows notebook

1 2 ms 5 ms 8 ms 192.168.1.254
2 2 ms 1 ms 1 ms 192.168.20.254
3 5 ms 2 ms 2 ms 137.189.161.252
4 2 ms 2 ms 2 ms 137.189.192.238
5 5 ms 4 ms 4 ms google3-10G.hkix.net [202.40.161.10]
6 4 ms 4 ms 4 ms 209.85.241.56
7 5 ms 5 ms 5 ms 216.239.43.17
8 14 ms 16 ms 17 ms 216.239.48.238
9 5 ms 5 ms 5 ms hx-in-f147.1e100.net [74.125.71.147]

192.168.20.51 id the address of my desktop in the lab network
192.168.20.254 is the gateway
in the adhoc network, 192.168.1.254 is my desktop

Thanks a lot for helping me!!

[Freston]

Welcome to the forums!

Perhaps this has something to do with your DNS settings?

Can you give the output of this command on your Linux box:

cat /etc/resolv.conf

And on the Windows box:

ipconfig /all

Also, what happens if you connect to google via IP address, rather than URL:
Google

[periz]

thanks!

the output of cat /etc/resolv.conf is
nameserver 192.168.20.196
nameserver 192.168.2.249
nameserver 137.189.192.3

in the windows notebook the DNS is 192.168.20.196,
manually set by me.

on the linux desktop, settings come from dhcp.

if I input the IP address of google, the loading speed is normal (very quick).
this means that yes, it is a problem of DNS, but the DNS should be the same in the two PCs, no?!?!?

and why problems just with google.com?

thx a lot!

[Freston]

if I input the IP address of google, the loading speed is normal (very quick).

Good news!

this means that yes, it is a problem of DNS, but the DNS should be the same in the two PCs, no?!?!?

Nope, both have different DNS servers. Or at least, the Wintel only has one DNS server and the other has three.

Your second nameserver in resolv.conf, that is a local nameserver? Because I'm not quite sure about your setup. Do you run local nameservers? And DHCP settings, where do they come from?

[periz]

y, local nameservers of the network of my lab
dhcp comes from the same network.
i don't know further details about this...
i can try to manually insert just 1 dns...
let me see

[Freston]

Oh, you're on a LAN?

Can you do this:

ping -c 4 192.168.2.249

That's the second nameserver, perhaps it's down?

What if you edit your resolv.conf to contain only the first nameserver? Then your Linux box is configured the same as the Wintel. This wont be persistent between reboots, but it may not have to be.

[periz]

y, the scond dns is down
i forced only 1 dns, but no changes.
and anyway, why does this problem happen just with google.com?!?!?!
and then, mozilla stucks on "connecting to" and not on "looking up"...

[periz]

i know nothing about ipv6: could this have something to do?

then I thought maybe it's an external appearance of the 2 machines, but I checked and, as expected, both appear on internet with the same IP...

[Freston]

y, the scond dns is down
i forced only 1 dns, but no changes.
and anyway, why does this problem happen just with google.com?!?!?!
and then, mozilla stucks on "connecting to" and not on "looking up"..

Heh, for the nameserver, contact your local administrator

As for the slowness of just google, well, DNS still has some mysteries to me but DNS servers have caches that can become corrupted, or perhaps (depending on settings) your machine thinks it needs to get certain DNS info from the downed server.
I know there are many options on both client and serverside on how to handle multiple DNS servers on a network, and how to prioritize them. Mostly as a user you don't notice this. But when something goes wrong it's always a bit of a puzzle.

The quickest fix is perhaps to get the downed server up.

And what I forgot to ask, did you have these problems before? Or was there a point in history when your Linux box connected properly to google? Or is everything new?

[Freston]

i know nothing about ipv6: could this have something to do?

No, IPv6 isn't an issue here. You're still running IPv4.

then I thought maybe it's an external appearance of the 2 machines, but I checked and, as expected, both appear on internet with the same IP...

Yeah, you're behind a NAT.

But there is the matter of subnet. You get every setting through DHCP right?
From memory, but Windows uses other default values than Linux (correct me if I'm wrong though)

But I would expect the Wintel to have a subnet of 255.255.0.0 and the Linux box 255.255.255.0

If this is the case, then you might want to change the Linux box's subnet to 255.255.0.0, because the second nameserver is probably unreachable (hadn't noticed that before...). To be fully sure, try to ping the second nameserver from the Windows machine:

ping 192.168.2.249